LONDON, April 16 (Reuters) - "What's your interest in Bill and Ben in the pick?"

While most people wouldn't understand the question, this is common vernacular for London currency traders active in the daily 4 o'clock "fixing" of global reference exchange rates.

A basic translation of that particular line of Cockney rhyming slang, originating in London's working class East End, would run something like: "Are you a buyer or a seller of dollar/yen at the daily benchmark rate-setting fix?"

The wisecracking, rhyme-based language that can make a "whistle" mean a suit (from "whistle and flute") or a "Barnet" mean hair (from "Barnet Fair") has been used by traders in the City of London for decades. But can a computer crack the code?

Financial regulators are now trying to translate such exchanges into plain English as they investigate whether dealers have colluded to rig benchmark foreign exchange rates used to price trillions of dollars' worth of deals.

Britain's financial watchdog, the Financial Conduct Authority (FCA), has 50-60 staff dedicated to the foreign exchange investigation, some of whom are former market participants who are helping to decode the traderspeak.

Banks now want to go one step further, and are looking at acquiring "Big Brother" technology that can spot and prevent inappropriate communication or fraudulent activity rather than piecing together evidence afterwards.

"There is a huge market for this right now," said Sang Lee, founding partner at Aite Group, an independent research and advisory firm focused on business, technology and regulatory issues in Boston.

Lee said the focus is on software that can monitor and understand the language traders speak in their electronic chats, instant messaging and emails, and alert the bank to potentially inappropriate communications or nefarious activity.

"For at least 12 months now, this has been one of the major focus areas for both market participants and the technology companies," he said.

Traders at banks and other financial institutions often communicate with each other via third-party chatrooms including those offered by Bloomberg LP and Thomson Reuters Corp. , parent of the Reuters news agency.

The world's biggest banks, Britain's FCA, the Bank of England and the U.S. Department of Justice are among those trawling through countless chatroom transcripts for evidence of questionable activity as part of a global investigation into the market.

Online communications featured prominently in a separate five-year inquiry into manipulation of an interest rate known as the London interbank offered rate, or Libor. So far 10 banks and brokerages have been fined a total of $6 billion in penalties, and charges have been brought against 13 individuals.

RELATIONSHIP FORENSICS

One of the technology companies that has gained from banks' increased vigilance is Digital Reasoning, based outside Nashville in the U.S. state of Tennessee.

Digital Reasoning's software can scan up to billions of communications from thousands of traders, spotting language patterns and raising a red flag to potentially dubious activity.

Rob Metcalf, the company's president and chief operating officer, told Reuters there has been a sharp increase in interest for this software from banks over the last six months, just as the global investigation has taken off.

"The big banks will drive this, and regulators are interested too. It will be a 'base-line' capability across major banks in two years," he said.

Metcalf says his firm is in "active conversation" with 10-20 of the world's leading financial institutions, particularly U.S. and European firms.

Reuters contacted UBS, Deutsche Bank AG , Credit Suisse AG, JP Morgan, Citigroup, Royal Bank of Scotland and Barclays to see whether they were buying such technology. None of the banks commented for this report.

Banks have been active in moving towards more sophisticated analytics across all forms of electronic communications over the last year, said Michael O'Brien, head of sales for SMARTS Broker market surveillance platform, part of NASDAQ OMX.

One area they are looking at is "relationship forensics", tracking traders' communications with each other to spot patterns that point to a close working relationship. These could include behaviour such as always copying a particular person on emails, or if someone always responds to a message or email within a couple of minutes.

That's because any dubious activity between two or more people is bound to be carried out by those who have a close relationship with each other, O'Brien said.

O'Brien estimates that 10-20 percent of a big investment bank's compliance operation is geared towards trading analysis and the detection of - and protection against - market abuse and trading related risk.

Banks are looking for software that is able not only to detect language patterns in traders' electronic communications, but to match that up with patterns detected across other media, such as social media profiles, Aite Group's Lee said.

"It's a huge challenge," said Lee, noting that the $5.3 trillion a day over-the-counter currency market operates 24 hours a day across all time zones and remains virtually unregulated.

Thomson Reuters runs one of the two dominant global currency trading platforms, along with ICAP Plc-owned EBS.

So far, more than 30 traders at many of the world's biggest banks have been placed on leave, suspended or fired as the global investigation has gathered momentum over the last six months. Even the Bank of England has suspended an employee.

No individual or institution has been accused of any wrongdoing. (Editing by Carmel Crimmins and David Stamp)